Electrical and mechanical properties of h-BN nanoplates on Ir(111) studied by STM and NC-AFM

Hexagonal boron nitride (h-BN) on metal surfaces is subjected to substrate interactions as well as in-plane strains resulted from the lattice mismatch between h-BN and the underlying substrate. Here, we investigate the electrical and mechanical properties of h-BN nanoplate grown on Ir(111) using a combined approach of scanning tunneling microscopy (STM), noncontact atomic force microscopy (nc-AFM) and density functional theory (DFT) calculations. The in situ synthesized h-BN nanoplates have a characteristic triangular shape with zigzag-type edges. Boron and nitrogen atoms can be identified by distinct chemical interaction with metallic tip. The nc-AFM images show a strong tip-dependent contrast, which transforms from honeycomb lattices to hexagonal spots by switching W-tip to Cl-tip. Based on DFT calculations, we interpret the contrast conversion in terms of a combination of tip dipole and charge transfer from Ir(111) surface to BN nanoplates bound to Ir(111). In addition, the elastic deformation of h-BN nanoplates was measured by nc-AFM force map and lateral stiffness of h-BN nanoplates dramatically depend on their size.